Rheostat



Patented June 5, 1923.

UNITED STATES PATENT OFFICE.

SOLOMON RITTER HIPPLE, OF WILLIAMSPORT, PENNSYLVANIA, ASSIGNOE T0 D. X. INSTRUMENT COMPANY, OF HARRISBURG, PENNSYLVANIA, A CORPORATION OF DELAWARE.

RHEOSTAT.

Application led September 6, 1922. Serial No. 586,433.

Y 1o all 'whom it may concerne Be it known that I, SonoMoN Rrrrnn H1r- PLE, a citizen of the United States, residing at the city of Williamsport, county of Lycoming, State of Pennsylvania, have invented certain new and useful Improvements in Rheostats; and I do hereby declare the following to be a full, clear, and exact description of the invention, suchfas will enable others skilled in the art to which it appertains to make and use the same.

The invention relates to a new and useful construction of rheostat adapted-to produce extremely line or delicate adjustments or regulations of electrical current, the instrument being particularly applicable to radio installations, -but in no sense limited to such application. To this end, the invention comprises an insulating casing containing a body-of granular conducting material, terminals located at opposite ends of said casing, with the granular material between them, one of said terminals being adjustable within the casing and havin associated. therewith a piston working wit in the casing and operating on the granular material to ap ly varying degrees of compressive force thereto, to increase or decrease the resistance to an electric current traversing the granular material, said adjustable terminal preferably having a pointed end, beyond the piston, which sti l further regulates the extent of contact of the terminal with the granular material and admits of the finest contact adjustments between the terminal and the granular material. These and other objects of the invention will be set forth in detail in the annexed specification, predicated on the accompanying drawings, in which Fig. l is a perspective plan view of the rheostat;

Fig. 2 is a plan view partly in section.

Referring to the drawings, l indicates a base, preferably formed of metal or other conductive material, having openings 2 at opposite ends thereof to permit the rheostat to be attached to a suitable support. such, for example, as the panel of a radio set. Projecting from the base 1 is a casing 3 of suitable insulating material, such, for example, as cartridge paper or the like, which will permit the inner end of the casing to be crimped inwardly, as at 4. Mounted within the casing 3 is a tubular sleeve 5,

`preferably made of glass or other suitable insulating material, to provide a smooth cylindrical bore, within which sleeve there is confined a body of'loose granular conducting material, such as coinminuted carbon, 0r a mixture of carbon and a suitable granulated metal. l

Mounted in a screw-threaded openin in the base 1 is a screw-threaded spindlge 7, which is adjustable longitudinally of the axis of the casing 3 and the tubular sleeve 5, said spindle preferably being provided with a tapered inner end, which contacts with the granular material 6, and havingon its outer end a handle'or knob 8 which is secured to the spindle by a suitable set screw 9. Secured to the spindle 7 near the inner end thereof is a piston 10, which may conveniently be attached to the spindle by means of a lixedwasher 11, which may be of metal soldered or brazed to the spindle, a movable washer 12 and a set-nut 13, the latter serving to clamp ther piston firmly in position and expand the same so that its peripheral surface will be in close engagementwith the interior of the tubular sleeve 5.

Mounted in the inner end of the housing, comprising the casing and the sleeve 5, is a lixed terminal comprising a spindle 15 preferably provided with a conical inner end projecting within the granular material, and a fixed collar 16, said spindle having a screw-threaded outer portion. Mounted on said spindle is a washer 17, preferably of metal, an insulating washer 18 fitting snugly within the tubular member 5, a washer 19 fitting within the casing 3 and resting against the end of the tubular member 5, a washer 20 adapted to overlie and engage the inturned or crimped end portion 4 of the casing 3, and nuts 21 and 22 which serve to confine the various washers on the spindle 15 and to clamp the crimped edge 4 of thc casing 3 firmly between the washers 19 and 20. d

As thus constructed, thc rheostat isadapted to be mounted on the panel of the apparatus to which it is applied, by lne-.ins of the base 2, so that the spindle 7 projects forwardly of the panel. The circuit in which the rheostat is interpolated is connected to the fixed terminal, preferably between the nuts 21 and 22, and to the movable terminal by connecting one end of the circuit wire under one of the screws which lll) thereof driven deeper `granular material.

secure the base 1 to the panel or support. Asthus applied, the rheostat is v.generally horizontal, so that when the spindle 7, which constitutes the movable terminal, is screwed outwardly, the piston l will recede from the granular material 6, and when the pressure on the latter is released, the portion thereof adjacent the piston 10 and the tapered end of the spindle will How forward in the tubular member until the surface of the material attains thev normal angle of iepose- If the pointed end of the spindle is then wholly out ofcontact-with the granular material, no current will flow. By turning up the screw spindle bymeans of the handle until the tip of the pointed end of the spindle just engages the surface of the granular material, the minimuincurrent will be permitted to pass, and the amount of current may be increased gradually and by very small increments as the spindle 7 is turned up, and the pointed end int-o the body of rl`he continued forward movement of the spindle T will causethe piston l0 to force the granular material in the tubular member 5 into a gradually compacted mass, the. resistance 4t-o the flow of the current between the terminals and through the granular material being inversely proportional to the degree of compression between the particles of the granuar material as imposed by the iston- It will be a parent, therefore, that t 1e Acurrent flowing tlrough the rheostatmay bevaried by practically infinitesimal amounts tween the limits of maximum4 and no-current, by proper adjustments of the movable terminal, and as the screw-threads on the spindle 't' are preferably very fine, it wilLbe apparent that `extremely delicate regula.- tion of the current, to meet the most exacting conditions, may be eiected, first, by the extent of engagement or contact between the relatively long ta ered end of the adjustable terminal an the granular material, and second, by the extent or deo'ree of coinpiession imposed on the granular material confined between the two terminals.

In order lo maintain the body of granular conducting material 6 in roperly loosened condition, there is pre erably mounted within the sleeve 5, and between the piston and the washer 18, a helical spring which is retained normally under compression. Any movement of the spring due to the adjustment of the terminal will serve to agitate the granular material and more the particles thereof relatively to each other, and prevent the particles being permanently compacted. lVhen the terminal 7 and piston 8 are retracted, the spring 23 expands longitudinally and the various convolutions thereof stir up and loosen the granular maierial. When the terminal 7 and the piston 10. arefadvanced, the spring 23: is compressed and the movement of the convolutions thereof alsoagitates and displaces the elements ofthegranularmaterial.- The spring 23 is l'n'eferably made off'non-conductive mate rial, or, if made of meta-l,- iscompletely coated with an insulating medium to prevent contact between the metal thereof and :in r of the conductive elements of the rheostat.

lVhat I claim is:

1. A rheostat comprisingv an insulating casing, abody of granular conductive :material therein, terminals' in said casing adapted to engage said granular material, one of said terminals being adjustable within the casing and having a piston thereon .for compressing the'granular material and a tapered end engaging said material.

rheostat comprising an insulating casing, a body ofgranular conductive material therein, a fixed terminalat one end. of the. casing, and. an. adjustable terminal at the other end having a piston thereon for compressing the granular material-and a tapered end engaging said material.

3. A. rheostat comprising abuse, a. tubular shell connected toA the base having an inwardly crimpedjouter end; a sleeve of'. insulating material .within the shell; a berininal iu one end of tlie shell includingl a threaded. spindle, a washer'on the spindle engaging the' top Aol the sleeve, a 4second washer on. the spindle .engaging the crimped end of4 the Vsleeve,.and a.nut. on 4the spindle to clamp ,thecrmpbetWeenthe waslieis; a terminalmounted in said..base und projecting within said sleeve, said terminal including a threaded-spindle engaging a threaded openingin Vthe.base.and.a piston fixed to said. s pindle:and slidable in saidsleeve; and a body of ranular material in said sleevebetween said terminals.-

l. A rheostat comprising a base, a tubular shell connected to the base having an inwardly crimped outer end, a sleeve of insulating material within the shell; a terminal in one end of the shell including :i threaded spindle, :i washer on the spindle engaging the top of the sleeve, a second washer on the spindle engaging the crimped end of the sleeve` and a nut on the spindle to clamp the crimp between the washers; a terminal mounted in said base andprojecting within said sleeve, said terminal including a.V taperended threaded spindle engaging a threaded opening in the base, and apiston fixed to said spindle and slidable in said sleeve; and a body of granular material in said=sleeve between said terminals.

lu testimony whereof I affix my Signature.

SOLOMON RITTER HIPPLE. 

